The present invention relates to novel, fluorine-containing cyclic compounds, fluorine-containing polymers prepared by polymerization or copolymerization of such compounds, and particularly to resist compositions used for vacuum ultraviolet wavelength region and patterning methods for making resist patterns.
Fluorine-containing compounds have been used or developed in various fields particularly in the field of advanced materials due to their good qualities (e.g., water repellency, oil repellency, low water absorption, heat resistance, weather resistance, corrosion resistance, transparency, photosensitivity, low refractive index, and low dielectric property). In particular, they are used in the coating field in view of their characteristic transparency behavior in each wavelength. Recently, there have been active researches and developments of (a) anti-reflection films taking advantage of their low refractive indexes and visible light transparency, (b) optical devices taking advantage of their transparency in long wavelength band (optical communication wavelength band), and (c) resist compositions taking advantage of their transparency in ultraviolet region (particularly vacuum ultraviolet region). A common aim in polymer design of such researches and developments is to achieve good adhesion to substrate and high glass transition point hardness), while achieving transparency in each wavelength for use by introducing as many fluorine atoms as possible. There are various proposals of increasing transparency at each wavelength by increasing the fluorine content in material design. However, there are few reports on improving fluorine-containing monomers themselves in hydrophilicity and adhesion and on obtaining high glass transition point.
Recently, in next generation F2 resist field of vacuum ultraviolet region, there were reports on a hydroxyl-containing fluorostyrene (see T. H. Fedynyshyn, A. Cabral et al., J. Photopolym. Sci. Technol., 15, 655-666 (2002)) and on a hydroxyl-containing fluoronorbornene compound (see Ralph R. Dammel, Raj Sakamuri et al., J. Photopolym. Sci. Technol., 14, 603-611 (2001)). Thus, there was emerged an idea of containing fluorine and making polarity of hydroxyl group coexistent in the molecule. However, compatibility between transparency in ultraviolet region and etching resistance is still insufficient, and there exist many factors to be improved. Furthermore, conventional fluorine containing norbornene compounds have an electron attracting group (e.g., fluorine atom and trifluoromethyl group) directly bonded to norbornene ring, thereby lowering electron density of a polymerizable double bond. Thus, there are problems of low yield and insufficient molecular weight in synthesis of the target polymers from the above norbornene compounds. Thus, conventional compounds are not necessarily sufficient in capability, and there has been a demand for creating novel monomers or raw materials capable of efficiently providing further improved polymers, which are free of the above-mentioned defects.